My idea scenario for continued testing of PostgresRegistry would be to have some kind of system that allows a few priveleged accounts (MW devs + jenkins) to request a temporary empty schema. This would involve some kind of API that allows the requestor to indicate when they're done with the schema, allowing it to be deleted (or cleared and reused, if, say, this is implemented as a fixed-size pool of persistent schemas). I could imagine in some cases the same requestor might want multiple schemas simultaneously to be used in concert (for tests on a multi-user Registry, for example). Most often, a suite of tests that could be run in parallel would ideally want to grab one schema for each (usually short-lived) test.
All of this is negotiable, of course, and there are other approaches that would let us add at least some test coverage for Postgres that would require less effort on the service side. I'm assigning this ticket to Christopher Stephens in the hopes he'll push us to at least keep discussing this and looking for a solution, and I figure we'll create different tickets if we decide to take a substantially different approach.